This invention relates generally to tubing clamps and particularly to a slide clamp which is employed to open and close the fluid passageway of flexible tubing.
Several types of slide clamps have been proposed in the prior art. For example, slide clamps fabricated from metal suffer numerous disadvantages, which principally include sharp edges which tend to cut both tubing and the person manipulating the clamp. Metal slide clamps also have a tendency to scissor or transversely twist from the desired perpendicular relationship to an undesirable parallel relationship with the tubing when the user slides those clamps open and closed. Consequently, metal slide clamps have proved to be impractical for repeated opening and closing of resilient vinyl, plastic or rubber tubing, both to the user during manipulation of the clamp and to the tubing itself.
Slide clamps fabricated from a plastic material have been proposed in an attempt to reduce the deleterious effects both to the tubing and to the user which are present with metal slide clamps, as described above. Although these clamps did reduce the hazards of cutting and scratching presented to a doctor or technician manipulating the clamp, it was found that large frictional forces made the manipulation of the clamp particularly difficult when the tubing is crimped shut into a narrow slot and reversably uncrimped and opened. Moreover, the tubing wall is oftentimes ruptured when these plastic clamps were employed to crimp the tubing closed.
When plastic tubing is transversely compressed into a narrow slot by a plastic or metal slide clamp, the constant pressure from the clamp causes the tubing wall to undergo "cold flow" or "plastic creep" in the immediate vicinity where the tubing is crimped. This phenomenon begins to occur within minutes from the time when the tubing is first crimped. After a short period, the cold flow of the tubing wall away from the crimped area results in an ineffective and weak closure of the tubing. U.S. Pat. No. 3,357,674 discloses a plastic slide clamp which is unable to compensate for the phenomenon of cold flow and is so difficult for the user to manipulate, that a thumb ring must be provided.
Overcoming the physical phenomenon of cold flow has posed great difficulties in disposable and inexpensive slide clamps heretofore proposed. The unreliable sealing characteristics and inability to compensate for cold flow has contributed to numerous hospital patient accidents. Cold flow produces an ineffective seal and may lead to "fluid flooding" which results from ineffective slide clamps proposed to date which are unable to compensate for unreliable sealing characteristics attributable to cold flow.
A plastic slide clamp has been proposed by Travenol Laboratories, Inc. which eliminates some of the problems present in prior clamps. That clamp has been employed for larger diameter rubber tubing having an internal diameter of greater than about 0.225 inches. For larger diameter tubing, the Travenol clamp reduces the tendency to scissor and the tendency to rupture the tubing wall present with prior proposed plastic slide clamps. However, the Travenol clamp suffers from the disadvantages described above when employed with plastic tubing having an internal diameter of less than about 0.225 inches.
The need is apparent for a plastic slide clamp which can be easily manufactured in different sizes for a variety of tubing diameters, is less difficult to manipulate, and is able to compensate for cold flow and maintain the tubing in a closed position to eliminate the dangers of fluid flooding.